A prospective and blinded investigation of magnetic resonance imaging of the knee. Abnormal findings in asymptomatic subjects.

To evaluate magnetic resonance imaging (MRI) of meniscal, ligamentous, and bony abnormalities in patients without clinical symptoms, scans were performed on 74 asymptomatic volunteers without histories or symptoms of knee injury. Before review by three radiologists in an independent and blinded fashion, the scans were mixed with 26 MRI scans from symptomatic patients. Sixteen percent of the asymptomatic volunteers had meniscal abnormalities consistent with a tear. The prevalence of MRI findings of a meniscal tear increased from 13% in individuals younger than 45 years of age to 36% in those older than 45. An additional 30% of the volunteers showed meniscal abnormalities consisting of a linear area of increased MR signal not communicating with a meniscal edge, which was not interpreted to represent a tear. The high incidence of abnormal MRI findings in asymptomatic subjects underscores the danger of relying on a diagnostic test without careful correlation with clinical signs and symptoms. These findings also emphasize the importance of access to relevant clinical data when interpreting MRI scans of the knee.